1. Technical Field
The present invention generally relates to metal-working rolling mills and, more particularly, to improved saddles that support the backing assemblies that support the second intermediate rolls of the mills. Specifically, the present invention relates to a saddle for a backing assembly in a cluster mill or a Z-mill wherein the saddle includes improved bearing surfaces that accommodate adjustments to reduce wear.
2. Background Information
Rolling mills such as cluster mills, 20-high cluster mills, and Z-high mills are known in the art for cold rolling metal strips. Exemplary mills are disclosed in U.S. Pat. Nos. 2,169,711; 2,187,250; 2,479,974; 2,776,586; 4,289,013; 5,471,859; and 5,481,895. These mills are commonly known as “Sendzimir” mills, “Z” mills or “Sendzimirs.”
A prior art cluster mill is depicted in FIGS. 1-5 of the present patent application. FIGS. 1-5 were originally described in U.S. Pat. No. 5,471,859 and substantial portions of this description are repeated herein for the benefit of the reader. A schematic view of a cluster mill 2 is shown in FIG. 5. Cluster mill 2 generally includes a pair of work rolls 12 that are supported by a set of four first intermediate rolls 13 which are in turn supported by a set of six second intermediate rolls including four driven rolls 15 and two non-driven idler rolls 14. A strip of metal 8 passes back and forth between work rolls 12 in order for metal strip 8 to be cold rolled.
The second intermediate rolls 14,15 are supported in turn by eight backing assemblies (identified as A, B, C, D, E, F, G, and H). Each backing assembly includes a plurality of roller bearings 30 mounted upon a shaft 18. Shaft 18 is supported at intervals along its length by saddles 19. Each saddle 19 includes a ring 31 and a shoe 29. Shoes 29 are mounted to a mill housing 10. An example of mill housing 10 may be found in U.S. Pat. No. 3,815,401. Saddles 19 also include eccentrics or eccentric rings 23 that are keyed to shaft 18 with a key 24. Each ring 23 includes a bearing surface at its outside diameter. As described below, the outer bearing surface of each ring 23 either directly engages the inner surface of saddle ring 31 or indirectly engages the inner surface of saddle ring 31. This arrangement provides radial motion of shaft 18 when shaft 18 or ring 23 is rotated.
The art generally labels backing assemblies A-H and the components of backing assemblies A-H as shown in FIG. 5. In FIG. 5 (the operator's side or front of mill 2), the left most upper assembly is labeled “A” and working clockwise around mill 2, the remaining assemblies are labeled “B” through “H.” This labeling convention is generally followed in the art and will be followed in this specification such that the labels A-H are applied to backing assemblies and the parts of each backing assembly.
In the case of backing assemblies A, D, E, F, G, and H, saddles 19 are known as “plain saddles” and rings 23 mount directly within saddle rings 31 and slide within rings 31 as shafts 18 are rotated. In these plain saddles, the outer bearing surface of ring 23 directly and frictionally engages the inner bearing surface of saddle ring 31. The direct frictional engagement between ring 23 and saddle ring 31 creates high frictional forces and does not allow shafts 18 to be adjusted under load (during rolling of metal strip 8). Rings 23A, 23D, 23E, and 23H are known as “side eccentrics.” Rotation of these side eccentric rings and these side eccentric shafts is used to adjust the radial position of their bearings (30A, 30D, 30E, and 30H) to take up wear on rolls 12-15.
Rings 23F and 23G are known as the “lower screwdown eccentrics.” Rotation of shafts 18F and 18G (along with rings 23F and 23G) can be used to take up for roll wear as described above, but is more frequently used to adjust the level of the top surface of lower work roll 12. This is known as “adjusting the pass line height” or “pass line adjustment.”
In the case of backing assemblies B and C, saddles 19B and 19C are known as “roller saddles.” In small mills that do not have a crown adjustment, the construction of backing assemblies B and C is the same as for the plane saddles, with the exception that a single row of rollers (similar to those shown at 37 in FIG. 3) is interposed between the outside of each ring 23 and the inside of the mating saddle ring 31. The addition of rollers 37 enables the shafts 18B and 18C and rings 23B and 23C to roll within saddle rings 31B and 31C. Rollers 37 reduce the friction sufficiently for adjustment to be made under load. This adjustment is known as the “upper screwdown” or “screwdown” and is used to adjust the roll gap (the gap between work rolls 12) under load. The adjustment is made by using double racks (not shown), one engaging gears 22 on shafts 18B and 18C at the operator's side, and one engaging gears 22 on shafts 18B and 18C at the drive side (see FIG. 4). Each double rack is actuated by a direct acting hydraulic cylinder, and a position servo is used to control the position of the hydraulic pistons, and so control the roll gap.
For larger mills and other newer small mills, provision is made for individual adjustment of the radial position of shaft, bearings, and eccentric rings at each saddle position. This type of adjustment is known in the art as “crown adjustment” and the prior art construction used to achieve “crown adjustment” is generally shown in FIGS. 1-4. On the B and C saddles, saddle rings 31 are provided with a larger diameter bore 32, so that a second set of rollers 33 and a ring 34 (the outside diameter of which is eccentric relative to its inside diameter) can be interposed between saddle ring 31 and rollers 37. Rings 34 are known as “eccentric rings” or “crown adjust rings.” A gear ring 38, having gear teeth 40, is mounted on each side of each eccentric ring 34 and rivets 39 are used to retain gear rings 38, eccentric 23, eccentric ring 34, saddle ring 31, and shoe 29, with two sets of rollers 33 and 37, together as one assembly, known as the saddle assembly 19.
As shown in FIGS. 1 and 2, a double rack 41 is used at each saddle location to engage with both sets of gear teeth 40 on each gear ring 38 on both B and C saddle assemblies 19. A hydraulic cylinder, or motor drive jack (not shown), is used at each saddle location in order to translate rack 41. In the example of FIG. 4, seven individual drives are provided with one drive positioned at each saddle location. These drives are known as “crown adjustment” drives. If one drive is operated, its respective double rack 41 moves in a vertical direction, rotating the associated gear rings 38 and eccentric rings 34. This causes radial movement of eccentrics 23 on shafts 18B and 18C at the saddle location on which the eccentric rings 34 rotate, and a corresponding change in the roll gap at that longitudinal location. When this occurs, shafts 18 bend to permit the local adjustment.
Cluster mills of the type described above and depicted in FIGS. 1-5 were designed to slowly shape metal strip 8 by passing strip 8 back and forth between work rolls 12 many times. In today's environment of international price competition, the cluster mills are being pushed beyond their design limits so that the shaping of metal strip 8 may be achieved with fewer passes through work rolls 12. For instance, cluster mill 2 may be designed to adjust the shape of metal strip 8 2% with each pass through work rolls 12. The industry is now running cluster mill 2 to change the shape up to 7% with each pass through work rolls 12. Using cluster mill 2 in this manner increases the wear on the elements of saddles 19 requiring the owners of cluster mills 2 to replace the parts of mill 2 on a frequent maintenance schedule. Specifically, rollers 37 and 33 (also referred to as needle bearings) are pinched by the large adjustments and driven against gear rings 38. When this type of wear occurs, the owner of cluster mill 2 must replace gear rings 38 and grind the appropriate bearing surfaces so that larger needle bearings (rollers 33 and 37) may be retrofit into saddle 19. In addition to worn gear rings and rollers 33 and 37, saddle shoes 29 become warped and must be replaced. This type of undesirable wear is likely to increase as the industry requires faster and faster mill times. The industry will continue to push existing cluster mills to perform shaping operations beyond the original design limitations of the mill creating more and more wear on saddles 19. The art thus desires a saddle configuration that accommodates this type of cluster mill operation in order to reduce wear. Such a saddle configuration must be able to be retrofit into existing cluster mills when the saddles are being repaired.